Attempts were made to trace the effect of organoclay (OC) on the rheological and mechanical behaviors of the low density polyethylene (LDPE)/ethylene-vinyl acetate (EVA) blends. To do this effectively, in addition to LDPE/EVA/OC system, pure LOPE and LDPE/EVA blends were also examined as model systems. The rheological behavior was determined by the capillary rheometer. Morphological characterization was also carried out using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and theoretical approach based on interfacial energies. Shear viscosity, tensile strength and elastic modulus of LDPE/EVA were found to decrease by increasing the EVA content, while for LDPE/EVA/OC ternary nanocomposites, such properties showed an increase by increasing the content of EVA. Such behavior was explained by the morphological characteristic of the system in which OC was mainly intercalated/exfoliated in the EVA phase. This morphological characteristic was corroborated by the XRD, TEM and interfacial energies data. POLYM. ENG. SCI., 50:1315-1325, 2010. (C) 2010 Society of Plastics Engineers